I had been looking for a solution to remotely monitor the level LP gas in my outside tanks with Indigo for years. I gave up waiting, and decided to create one myself. I'm happy to say that it has been working quite reliably for a year now. I can see my tanks' level (as a % full value) on my control page, and get text alerts when the level passes thresholds I choose, and also when the propane company comes and refills it while I'm away.
This solution operates over ZWave and requires two special hardware items, a MimoLite, and an R3D Hall Effect Module. More detail in the attached document.
Please note that I am not an electrician or plumber. I believe this implementation is very safe, and the R3D device is intrinsically safe, per the Rochester specifications. Having noted that, install this solution at your own risk. Please feel free to contact me if you find any information you feel is incorrect.
Unzip the archive.
The PDF file contains the instructions, and the read_lp_tank_level.py file contains a python script.